The present invention relates to a radiation detecting arrangement for counting an ionizing radiation by means of a radiation detector of tubular form comprising a compensating filter arrangement.
Radiation detectors for counting or measuring an ionizing radiation, under the effect of this radiation, produce electric signals whose magnitude is a measure of the dose rate of the ionizing radiation acting upon the radiation detector. In order to be able to make the magnitude of these electric signals independent of the energy or of the energy and the direction of the ionizing radiation acting upon the radiation detector, a compensating filter or a compensating filter arrangement is arranged around the radiation detector, in particular around the active volume thereof. The compensating filter arrangement is so constructed that it, in the energy spectrum of the radiation, will strongly absorb such radiation components which, at the same dose rate, will trigger a greater electric signal in the radiation detector. In addition, ionizing radiations from directions from which they, at the same dose rate, would trigger a signal of smaller magnitude in the radiation detector, are less absorbed.
A radiation detecting arrangement of the type mentioned hereinbefore, is known, for example, from German Patent DE-OS No. 2,814,091. This prior art radiation detecting arrangement comprises a merely slightly absorbing supporting tube surrounding a radiation detector of tubular construction on the outside of which a number of different annular and sleeve-shaped filter parts are arranged. For establishing the desired absorption curve of the prior art radiation detecting arrangement, fixed spacings are provided for between the individual differently constructed filter parts. For fixing these spacings, for example, spacing rings are provided for in the prior art radiation detecting arrangement.
It has proved, however, that the manufacture of prefabricated ring-shaped filter parts having the shape required for manufacturing a radiation detecting arrangement of the type mentioned hereinabove, is extremely uneconomical in many cases, because the filter parts can only be injection-molded or cast. The filter parts are mostly made from a material which flows when being subjected to pressure. Therefore, they are unsuitable for being chucked or clamped for permitting a stock-removing machining.